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elements of life > absorption and emission spectra > Flashcards

absorption and emission spectra Flashcards

1
Q

what does spectroscopy mean

A

the study of how light and matter interact

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2
Q

what is light a form of according to the wave theory

A

electromagnetic radiation

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3
Q

describe the wave theory of light

A

it behaves like a wave with a characteristic wavelength and frequency. a wave of light will travel the distance between two points at a certain time

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4
Q

what is the speed of light when in a vacuum

A

3.00 x 10^8

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5
Q

what does wavelength mean

A

measures the distance travelled by the wave during one cycle (metres)

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6
Q

what does frequency mean

A

how many cycles a wave goes through every second and is measured in s-1 or hertz (Hz)

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7
Q

what do you get when you multiply wavelength and frequency together

A

a constant (the speed of light)

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8
Q

the equation that links speed of light, frequency and wavelength together…

A

speed of light (3 x 10^8) = wavelength (m) x frequency (Hz)

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9
Q

name the electromagnetic spectrum

A

radiowaves
microwaves
infrared radiation
visible light
ultraviolet
x rays
gamma rays

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10
Q

from top to bottom of the EM spectrum what happens to the wavelength and frequency

A

wavelength decreases
frequency increases

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11
Q

what is the particle theory of light

A

light is a stream of energy called photons. the energy of photons is related to the position of light in the EM spectrum

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12
Q

what is planck’s constant

A

6.63 x 10^-34 JHz^-1

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13
Q

what is the equation that links both the wave theory and the particle theory

A

difference in energy between two shells = frequency x plancks constant

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14
Q

what can a substance do under certain conditions

A

absorb or emit electromagnetic radiation in a characteristic way

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15
Q

what can analysing EM radiation enable us to do

A

identify a substance or find information about its structure and the way atoms are held together

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16
Q

what happens to atoms when they absorb energy

A

they become excited.

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17
Q

what happens when excited atoms lose energy

A

they return to their ground state and emit some sort of EM radiation (IR, visible light, UV) the emitted light can be split using a prism

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18
Q

what is meant by excited state

A

a quantam state higher than that of the ground state

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19
Q

what is meant by ground state

A

the lowest stable energy of a system (nucleus, molecule, ion or electron)

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20
Q

how does emission spectra form

A

from light emitted by excited electrons in the visible region

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21
Q

what does an emission spectra consist of

A

a series of coloured lines on a black background

22
Q

why is a continuous spectrum not produced

A

the atoms can only emit certain precise frequencies

23
Q

what does white light contain

A

all the visible wavelengths and its spectrum is normally continuous

24
Q

what happens when white light is passed through the sample

A

black lines appear in the continous spectrum which correspond to the lgiht that has been absorbed by the atoms in the sample. they also correspond with the coloured lines the emission spectra of the same element

25
Q

why is it called absorption spectra

A

it comes from light absorbed by atoms

26
Q

what does an absorption spectra look like

A

black lines on a coloured background

27
Q

describe the sequence of lines in an atomic spectra

A

it is characteristic of the atoms of the element that gave rise to it. it can be used to identify the element even when the element is present in a compound or part of a mixture

28
Q

what does the intensity of the light provide

A

a measure of the elements abundance

29
Q

why is the lyman series

A

the hydrogen emission spectra in UV light. it has a characteristic emission specturm in the UV region of the EM spectrum

30
Q

what is the Balmer series

A

hydrogenb emission spectrum in the visible light region

31
Q

what happens as a result of interaction of light and matter

A

the emitted frequencies of an element matches with the absorption frequencies of the same element

32
Q

what is atomic spectra caused by

A

electrons in atoms moving between different energy levels. when an atom is excited, electrons jump into higher energy levels, then drop back into the lower levels again and emit the extra energy as EM which gives an emission spectrum. when white light passes through a prism through a cool sample of a gasesous element , black lines appear in the continous absorption spectrum. these correspond to the light that has been absorbed by the atoms in the sample

33
Q

what does Bohrs theory give

A

a model for the electronic structure of atoms

34
Q

what is quantum theory

A

the electron in the hydrogen atoms exists only in certain definite energy levels or electron shells. a photon of light is emitted or absorbed when electron changes from one energy level to another. the energy of the photon is equal to the difference between the two energy levels

35
Q

what is the frequency of absorbed or emitted light related to and how

A

since energy of a photon = frequency x plancks constant then that means the frequency of the absorbed or emitted light is related to the difference in energy by change in energy - frequency x plancks constant
—> change in E = hv

36
Q

what can’t the energy of electrons change continuously

A

energy is quantised - electrons can only posess definite quantities of energy

37
Q

what do the rings around an atom represent

A

the energy levels of the electron

38
Q

the further away from the nucleus the electron is..

A

..the higher the energy levels of the electrons

39
Q

what do the frequencies of the lines of the Lyman series correspond to

A

changes in electronic energy from various upper levels to one common lower level. each line corresponds to particular energy level change

40
Q

what happens as energy levels increase

A

the levels become more closely spaced till they converge. after this point, it corresponds to the electron escaping from the atom and the electron is free to move around without any energy

41
Q

what is ionisation

A

losing electrons to become a positive ion

42
Q

what is the ionisation energy

A

the energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to produce 1 mole of gaseous +1 ions

43
Q

what are electron shells also called

A

energy levels

44
Q

what do glowing regions of all stgars emit

A

all frequencies of EM radiation between UV and IR

45
Q

what does the sun mainly emit

A

visible light. other stars emit UV radiation

46
Q

what happens when an element is heated strongly

A

the elements begins to glow, indicating that it is emitting energy in the visible region of the spectrum.

47
Q

electrons that have absorbed energy…

A

..have been promoted to a higher energy state

48
Q

what happens when electrons revert to a lower energy state

A

they lose energy by emitting photons whose energy corresponds to the energy loss

49
Q

what happens as frequency increases

A

the spectral lines get close together. this suggests the electronic energy levels get closer the more distant they become from the nucleus of an atom

50
Q

what dont two elements have the same emission spectra

A

because they have different numbers of protons, and different numbers and arrangements of electrons. The differences in spectra reflect the differences in the amount of energy that the atoms absorb or give off when their electrons move between energy levels.

51
Q

what does spectra provide evidence for

A

atomic structure

52
Q

how are electrons excited to higher energy levels

A

by heat or electricity

elements of life (15 decks)

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